چكيده به لاتين
Reducing energy consumption in the chlor-alkali industry is of great importance from the economic and environmental point of view. The use of oxygen-depolarized cathodes leads to a significant reduction in energy consumption in the membrane chlor-alkali process. In this regard, single atom electrocatalyst of non-precious metals was used to make oxygen-depolarized cathode. Initially, density functional theory calculations were used with the help of VASP software to select suitable non-precious metals (scandium, titanium, vanadium, manganese, iron, nickel, copper). Calculations showed that copper had the lowest overpotential (equal to 0.71 V) compared to other metals. Next, copper single atom electrocatalyst was synthesized by pyrolysis method for oxygen reduction reaction. Types of voltammetry tests, electrochemical impedance spectroscopy, chronoamperometry and types of characterization tests including field emission scanning electron microscope, transmission electron microscope, infrared Fourier transform spectroscopy, X-ray diffraction spectroscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy for the synthesized Cu SA/N-C electrocatalyst Commercial Pt/C 20%w/w were performed. The tests showed that the Cu SA/N-C electrocatalyst was comparable to the commercial electrocatalyst in terms of performance and stability. The synthetic electrocatalyst had the initial and half-wave potentials of 0.90 and 0.80 V, respectively, and these values for the commercial electrocatalyst were 0.95 and 0.85 V, respectively. Also, the synthetic electrocatalyst was able to advance the optimal four-electron path of oxygen reduction (electron transfer number = 4) compared to the commercial electrocatalyst (electron transfer number = 3.94). After 10 hours at a constant potential of 0.4 V, the current density in the synthetic and commercial electrocatalyst reached 83.6% and 96.36% of their initial value, respectively. After the synthesis of the optimal electrocatalyst, the oxygen-depolarized electrode was made from the synthetic electrocatalyst and commercial Pt/C 20%w/w with the same loading and evaluated in the advanced chlor-alkali cell with zero gap design under the temperature of 80℃ and humidity of 95%. During the tests performed in the advanced chlor-alkali cell, the oxygen-depolarized electrode with synthetic electrocatalyst has a voltage of 2.1 V and the sodium hydroxide current efficiency is 93.8% in 1 kA/m2, which are equal to the oxygen-depolarized electrode with commercial electrocatalyst, 1.9V and 100% is achieved, respectively.
